The invention relates to hearing aids, and more particularly relates to high-gain hearing aids. In its most immediate sense, the invention relates to high-gain hearing aids which reduce the occlusion effect.
Patients with severe hearing loss require high-gain hearing aids. Such aids use high-power amplification circuitry. Conventionally, such circuitry uses comparatively large electrical components. For this reason, high-gain hearing aids are conventionally of the behind-the-ear ("BTE") type.
However, such aids suffer from a serious limitation. This is that as the gain of the aid is increased, electroacoustic feedback also increases. This is because the hearing aid microphone and receiver are mechanically coupled to each other because both are mounted to the same housing. As a result, the gain of the aid is limited by the electroacoustic feedback.
In the past, efforts have been made to reduce electroacoustic feedback by physically separating the microphone and the receiver used in the hearing aid. For example, The Volta Review 1-80 pp. 40-44 describes a hearing aid in which the receiver is separated from the main body of the aid and mounted in an earmold that in turn is placed in the patient's ear.
While such a hearing aid would reduce electroacoustic feedback, it would be commercially unacceptable. This is because such an instrument would cause the patient to experience the occlusion effect, which is the plugged, sensation caused by the introduction of e.g. an earmold in the outermost portion of the ear.
It would therefore be advantageous to provide a high-gain hearing aid that has reduced electroacoustic feedback characteristics while nonetheless being constructed to reduce or eliminate the occlusion effect.
In accordance with the invention, there is provided a hybrid BTE and completely-in-canal ("CIC") hearing aid. A hearing aid in accordance with the invention has two components: a BTE component and a CIC component. These components are mechanically isolated from each other. The BTE component, which is mounted behind the ear, contains the microphone, the battery and the amplifier circuitry. The CIC component, which is shaped to fit into the ear canal of the patient in such a manner as to touch the bony portion of the ear canal, contains the hearing aid receiver, which is connected to the amplifier means.
Because the BTE and CIC components are mechanically isolated from each other, electroacoustic feedback is greatly reduced. This permits the gain of the hearing aid to be greatly increased and thereby made more suitable for patients with severe hearing loss. Additionally, because the CIC component is located so deep in the patient's ear canal as to touch the bony portion, it does not cause the patient to experience the occlusion effect. Therefore, a patient with severe hearing loss who uses a hearing aid in accordance with the invention can benefit from a higher gain without suffering from the occlusion effect.